Explosive fragmentation of porous solids

ABSTRACT

Porous solids having surface area of at least five square meters per gram are reduced to smaller particle size by explosive fragmentation. Exemplary disclosure concerns aluminosilicate zeolites in extremely finely divided form prepared by detonation of crystalline zeolites having adsorbed therein explosive compounds and compositions. In one particular embodiment, finely divided zeolite catalyst is supplied to the reactants and energy is furnished to the system by detonation of explosive-loaded crystalline zeolites within the reaction mixture. In addition, the products of detonation may afford reactants.

United States Patent 1 Rosinski 1 Feb. 13, 1973 [54] EXPLOSIVEFRAGMENTATION OF POROUS SOLIDS [52] US. Cl I ..241/1, 102/23 [51] Int.Cl ..F42d 1/00 [58] Field of Search ..241/1, D16. 9; 102/22, 23

[56] References Cited UNITED STATES PATENTS 2,826,369 3/1958 Haltmeier..244/1 2,867,172 l/1959 l-lradel ..102/24 HO 3,207,447 9/1965 Whiteham..244/1 OTHER PUBLlCATlONS Explosive Shattering of Minerals, John Cross,received US Patent Ofiice Feb, 1934, page 19 relied on.

Primary ExaminerVerlin R. Pendegrass Att0rney0swald G. Hayes and AndrewL. Gaboriault [5 7] ABSTRACT Porous solids having surface area of atleast five square meters per gram are reduced to smaller particle sizeby explosive fragmentation. Exemplary disclosure concernsaluminosilicate zeolites in extremely finely divided form prepared bydetonation of crystalline zeolites having adsorbed therein explosivecompounds and compositions. In one particular embodiment, finely dividedzeolite catalyst is supplied to the reactants and energy is furnished tothe system by detonation of explosive-loaded crystalline zeolites withinthe reaction mixture. In addition, the products of detonation may affordreactants.

4 Claims, No Drawings EXPLOSIVE FRAGMENTATION OF POROUS SOLIDS CROSSREFERENCE TO RELATED APPLICATIONS This application is a division of ourcopending application Ser. No. 828,733, filed May 28, 1969, and now U.S.Pat. No. 3,620,965.

BACKGROUND OF THE INVENTION 1. Value of the Invention An importantproperty of porous solids employed as absorbents, catalysts, catalystsupports and the line is diffusivity, i.e., the rate at which gases andliquids may diffuse into the pores for access to sorbent or catalyticsurfaces. The limiting effect of diffusivity is mitigated by the use ofsmaller particles than have heretofore been available because of shorterdiffusion paths over which the property is effective. Grinding to reduceparticle size becomes extremely expensive below size of a few micronsand produces irregularly shaped particles.

This invention is concerned with manufacture of porous solid particlesin finely divided form by detonation of porous materials, of whichcrystalline zeolites are exemplary, the pores of which are loaded withexplosive composition. More particularly, the invention provides highlyefficient catalysts which avoid diffusion limitations and providemaximum availability of catalytic surfaces. In some cases, the inventioncan supply energy for endothermic catalytic reactions by a technique inwhich theexplosive loaded zeolite catalyst is detonated within thereaction mixture. The products of detonation can be the source ofreactant substances such as oxides of carbon, nitrogen or both and mayalso apply desired high pressures for reactions favored by elevatedpressure.

2. Description of the Prior Art Zeolitic porous crystallinealuminosilicate has achieved wide recognition as a raw material in themanufacture of catalysts having unusual activity, selectivity andstability. A very large proportion of the cracking catalysts used in theUnited States and abroad is now constituted by highly active zeolites incombination with other substances which coact therewith to providecatalysts of unusually valuable properties.

The zeolitic catalysts have been described for a large number ofreactions including cracking, hydrocracking, hydroforming, reforming,alkylation, isomerization, disproportionation, hydration of olefins,amination of olefins, oxidation, dehydrogenation, dehydration ofalcohol, and desulfurization, among others. For many reactions thezeolite is activated by an ion exchange procedure which replaces theoriginal cations, usually sodium, with other cations having stabilizingor activating functions or both. In some cases additional catalyticagents are incorporated within the internal pores or associated with thezeolites externally of the thermal absorption area. An important exampleis impregnation or combination of active zeolites with ahydrogenation-dehydrogenation catalyst for use in such reactions ashydrocracking. This invention contemplates utilization of thesemodifications, known to the prior art. An apt summary of the types ofmodifications which can be achieved by ion exchange and by combinationwith other catalytic agents is described in U.S. Pat. No. 3,140,252granted July ll, 1964.

Although the newer crystalline zeolites have rapidly assumed prominencefor catalytic, absorbent and other utility or porous solids; the older,primarily amorphous adsorbents, catalysts and catalyst carriers arestill of very great commercial importance. All classes of thesematerials have diffusivity limits which frequently must be considered inany proposed use. This is true of silica. gel; alumina gel; mixed gelsor precipitates such as silica-alumina, silica-thoria,silica-alumina-zirconia; adsorbent clays in either natural or acidtreated form; animal and vegetable chars and the like. On occasion thesehave been reduced in particle size, as by grinding. It has also beenproposed to break down .the size of lumps of such materials as hydrogelsof silica, silica-alumina and the like by freezing before removal of theaqueous phase of the gel as formed.

A more recent development involves applying a crystallizable liquid todehydrated porous solids, inducing crystallization of that liquid andthen applying a second liquid which induces fragmentation of theparticles which bear crystals of the first liquid within their pores.That technique is described in U.S. Pat. No. 3,383,056 granted May 14,1968 to Leonard C. Drake.

SUMMARY or Tl-IE INVENTION This invention provides a unique measure ofcontrol over those properties of porous solids having influence onadsorptive and catalytic effectiveness which are related to the physicalproperties, primarily size and surface outside the pores of such solidsused for catalysis or adsorption. By variation in the degree of loadingwith explosive compositions, Zeolitic crystals and other porous solidsmay be fractured to almost any desired tially micron to colloidal insize. In many instances their dimensions are detectable only by lightscattering techniques.

In many catalytic reactions, it will be found desirable to accomplishdetonation and shattering in the reaction mixture to be catalyzed by thefinal product. This is of significant advantage in such operations ascracking of hydrocarbon fluids in that the energy released by detonationsupplies some, or all, of the endothermic heat of reaction.

The products of detonation also furnish some or all of the reactants.Also, detonation is competent to furnish some or all of the pressurewhich could promote interaction.

The freshly shattered product shows highly reactive sites at points ofcleavage between atoms of the original particle, particularly in thecrystalline zeolites where such cleavage is between atoms of the crystallattice.

- These highly active sites can be caused to react with the surface ofthe fractured solid. Means are thus provided which offer a possibilityfor manufacture of organic silicon and silicate compounds of highstability. For example, ethyl silicate compounds are useful as paintvehicles or paint binders.

DESCRIPTION OF SPECIFIC EMBODIMENTS The process is advantageous inmaking available, generally without the use of grinding equipment, fluidsize particles, e.g., particles of such small size that they may beapplied as a colloidally dispersed adsorbent or catalyst. The process isalso useful for the preparation of various sols of diverse utility.Other advantages will become apparent from the ensuing description.

Considering the invention in greater detail, the porous material ofwhich the granules are made may be of any chemical composition, organicor inorganic, and may have any utility. It is of course essential thatthe granules are porous in order that the explosive material may haveaccess to the interior thereof. Specific solids include silica gel,alumina, silica-alumina, oxides of calcium, barium, nickel, iron, andthe like. Gel-type solids are useful, as obtained by drying hydratedoxides such as alumina, silica, titania, zirconia, magnesia and zincaluminate. Also the zeolites, both natural and synthetic, and includingthose zeolites which act as molecular sieves having pores of uniform andgenerally very small size, say about 4 to 15 Angstroms. Ion exchangeforms of zeolites are suitable. Other solids are siliceous earths suchas natural clays and clay-like materials such as kaolin andmontomorillonite clays, bentonite, fullers earth, Superfiltrol, bauxiteand Porocel; porous ceramic materials such as unglazed procelain;aluminum silicate selective adsorbents such as calcium aluminumsilicate; activated carbon, bone char, charcoal, graphite,hydrosilicates, particularly those of aluminum. In general, the solid isan inorganic material, this term being employed in a sense sufficientlybroad to cover activated carbon, graphite, charcoal and bone chars whichare essentially carbon, even though in some cases they may contain smallamounts of hydrogen, oxygen, and other chemicals.

The preferred solids are inorganic, highly porous, and have a surfacearea greater than 15 square meters per gram. More generally, the surfacearea may vary from 5 square meter per gram to any desired upper limit;usually it may range from 5 to 700, and preferably from 50 to 300 or 400square meters per gram. As is known, these high surface areas are theresult of an internal effect, rather than merely the state ofsubdivision, and more particularly arise from the presence in the solidsof numerous pores or micropores which may have diameters in the range of3 or 4 Angstroms to 100 microns, preferably 5 Angstroms to 2 or 3microns. The pore volume is about 5 to 70 percent, preferably to 50percent, of the solids, and usually is greater than 0.2 cc. per gram.Microporous solids are preferred, the term microporous referring toporous, solid materials having at least percent of the total pore volumecomprising pores having diameters less than 100 Angstroms.

The preferred porous granules are crystalline zeolites such as zeolitesX, Y, A; erionite faujasite and offretite. The invention is alsoapplicable to porous solids in which the porosity or microporosity isdeveloped therein by steps comprising controlled precipitation,gellation, drying, and calcining of inorganic hydrous oxides or mixturesof oxides. The hydrous gels resulting from the gellation step maycontain foreign particulate matter dispersed therein in finely dividedstate. After drying and calcining, the gel granules will contain bothmicropores and macropores. It is found that in granules such as thesethe porosity tends to be more or less homogeneous. Less preferred aregranules, such as compacted tablets or extruded pellets, formed bycompressing finer granules, these materials lacking a structuralhomogeniety, and leading to less preferred results when treatedaccording to the invention.

It is desirable that the granules be as free as possible from moisture.If moisture is present, it may be removed at the outset by heating thegranules to a temperature in the range of 200 to 1,000F., or higher, todrive absorbed and/or adsorbed water from the internal pores. Suchheating may be done in conjunction with the application of reducedpressure to remove the moisture; or in place of reduced pressure, aflowing stream of inert gas may be employed to help remove the moisture;or the heating may be done in a stationary atmosphere.

The production of subdivided particles is favored if the starting solidsare already in a partially subdivided form, i.e., are available asparticles, by which is meant solid material having any suitable shapeand having a size suitably in the range of lp. to 50 mm., nominaldiameter, preferably 2p. to 20 mm.

The degree of fragmentation is controllable by selection of an explosivewith regard to rate of propagation of the explosive reaction and bycontrol of amount of such explosive composition. Inert materials such asinorganic salts may be added to further control rate and violence of theexplosion.

Generally, the explosive is impregnated into the pores from the liquidphase which may be the explosive itself or a solution thereof. It isgenerally that the explosive be restricted to that inside the poresalthough amounts of explosive outside the pores are helpful inpropagating the detonation when very small internal concentrations areemployed.

Suitably the particles are brought in contact with the impregnatingliquid, as by immersion, at a convenient temperature so that they imbibethe liquid until the pores are at least partially or completely filled.The immersion time is variable, but preferably is long enough to permitthe particles and the liquid to reach an equilibrium. Then the particlesare suitably separated from the excess liquid as by decantation,filtration, centrifugation, and the like. Alternately, the particles canbe contacted with only the amount of liquid required to give the degreeof loading. Prior to loading, these particles could be evacuated tofacilitate easy access of the loading liquid to the internal pores ofthe solids.

The various types of catalysts adsorbents and the like derived fromcrystalline aluminosilicate zeolites have been widely described inrecent patents and technical literature. These will not be" reviewed indetail. Reference is made to Advances in Catalysis, Vol. 18, pages259-371 by P.B. Venuto and P. S. Landis on Organic Catalysis overCrystalline Aluminosilicates.

According to the invention, such materials are loaded with an amount ofexplosive composition which will achieve a degree of fragmentation bestsuited for each particular application. In general, the zeolites loadedwith such explosive compositions are relatively stable, the zeoliteserving for this purpose somewhat the same function as diatomaceousearth in dynamite. Nitroglycerin is a preferred explosive but theinvention contemplates use of any material capable of explosivereactions such as nitrocellulose, trinitrotoluene, picric acid, ammoniumnitrate, combinations of perchlorates, chlorates and nitrates withcombustible materials such as carbon deposited in the pores bydecomposition of hydrocarbons or carbohydrates.

The explosive composition may be loaded in the pores as such or may beformed by reaction in the pores as for example by absorbing glycerin,toluene, or olefins into the pores and nitrating the absorbed materialby reaction with nitric acid or other suitable nitrating compounds.

Amounts of explosive composition as low as l percent of the zeolite maybe employed where there is a need for fairly large fragments. Forexample, a rare earth acid X may be caused to adsorb as little as lpercent wt. of nitroglycerin which upon detonation by heat is fracturedto a relatively minor extent for use in conventional catalysts such asthat described in U.S. Pat. No. 3,140,253 granted July 11, 1964. Ifthefracturing is not too extensive, the parts will retain shape selectivecharacteristics and be suitable for use in place of the type describedin U.S. Pat. No. 3,140,322 granted July 11, 1964.

More extensive fragmentation results as the particles are loaded withexplosive composition to greater proportion of their adsorptioncapability. Loading to at least 25 percent of the available capacitywould be required for extensive fragmentation. When fractured sodrastically, shape selective zeolite particles will tend to lose shapeselective properties. Erionite for example, can be so fragmented thatthe parts will show full or nearly full catalytic effects with respectto molecules too large to penetrate normal erionite crystals.

When it is desired to utilize the energy of detonation for supply ofheat of reaction or for vaporization of reactants, care is recommendedto assure that detonation of one portion of catalyst supply does notdetonate the reserve source, if any, for supply of explosiveloadedzeolite from which a portion of catalyst is supplied to the reaction. ingeneral, detonation within a reaction is induced by heat. A portion ofexplosiveloaded zeolite is abruptly introduced to a mass of reactantwithin a confined zone. This is effectively achieved, for example, byprojecting an encapsulated portion of explosive loaded zeolite throughan induction passage communicating with the reaction zone. Preferably,the encapsulating material has insulating properties to delay detonationfor a suitable period after introduction.

In a hydrocarbon cracking reaction, the encapsulated material canadvantageously be a high molecular weight, high melting point organiccoating about the pellet of zeolite fines. The wax or other highmolecular weight, high melting point coating can constitute a supply ofadditional reactant to the zone. As the coating melts and the pellet ofintroduced zeolite reaches detonation temperature, the individualzeolite crystals are fragmented and dispersed through the reaction zoneby explosive forces. The energy released by explosion is absorbed by theoil reactant for the cracking reaction.

When it is desired to prepare the fragmented zeolite outside thereaction zone, the explosion is conducted within a suitable enclosure.Forexample, a supply of explosive loaded zeolite is placed within aheavy walled plastic bag. Detonation can be accomplished by a highresistance wire to which current is supplied after the bag is closed orby any of the other means known to cause detonation of the particularexplosive employed, for example, concussion.

Such prefractured zeolite material may be introduced directly as aslurry in a reaction material by adding the finely divided catalystparticles to a reaction stream or to a stream of inert diluent added tothe reactor. The finely powdered catalyst is also capable of dispersionin gaseous streams. For example, in reactions which employ hydrogen, thefine catalysts may be dispersed in the gaseous hydrogen supplied to thereactor. Depending upon the character of the reaction, the totalproducts of explosion may be introduced to the reaction zone providedthat the reaction products are either reactants or relatively inert. Ingeneral, the gaseous products of reactions will include water, oxides ofnitrogen and oxides of carbon.

Alternately, the products of detonation can also furnish the necessarypressure in a sealed reactor to promote catalytic reaction with thecatalytic fragments or they can be used to furnish the pressure toaccelerate catalytic reaction between mixed components, such asoxidation, nitrating, fluoriding, etc.

Often, it will be found desirable to detonate the explosive-loadedporous solid in an inert liquid or in admixture with an inert solidwhich will melt or vaporize at the conditions of detonation thusabsorbing at least part of the energy released by detonation throughheat of vaporization, heat of fusion, or both of the inert materials.Use of such material which is in vapor phase after detonation simplifiesseparation because the fragmented solid may be settled and the vaporphase bled off at temperatures high enough to avoid reliquefaction.

The prefractured fine particles of zeolite may be composited in a matrixmaterial according to the system described in U.S. Pat. No. 3,140,249granted July ll, 1964. The finely fragmented material is advantageouslycollected by washing the explosion zone with water or other vehicle thusproviding slurry of the prefractured zeolite for addition to matrixmaterials.

In some particular embodiments of the invention, specific catalyticmaterials can be prepared according to the following examples:

EXAMPLE 1 A crystalline aluminosilicate of the faujasite type having asilica-alumina ratio of 2.5 (commonly called Zeolite X) is exchangedwith an aqueous solution of mixed rare earth chlorides at F until thesodium content of the zeolite is reduced to 0.5 wt. percent, dry basis.The rare earth content calculated as oxide is 27.7 wt. percent, drybasis. The rare earth exchanged zeolite (REX) is then washed free ofsoluble salts and dried in air at 230F. The dried zeolite crystals areimmersed in a saturated solution of nitroglycerin in ether, drained freeof liquid and vacuum dried at room temperature to remove the solvent.One gram of the explosive loaded zeolite is gently placed into a gelatincapsule which is then encapsulated by low melting point wax (120F).

One-hundred grams of Mid-Continent light gas oil is heated by anelectric mantle while enclosed within a steel bomb of 1 liter capacityfitted with a vertical tube for introduction of the catalyst. Thecatalyst pellet encapsulated in the wax is placed in the upper end ofthe tube above a valve external to the bomb and the end of the tube isthen closed by a threaded fitting. Upon opening of the valve below thecatalyst pellet, the latter is dropped to the oil charge maintained at800F. The temperature and pressure rise sharply after the explosive isdetonated. Upon cooling the bomb and removing the contents, it is foundthat extensive cracking has occurred to produce gasoline boiling rangeproduct.

EXAMPLE 2 A crystalline aluminosilicate of the faujasite type having asilica-alumina ratio 2.5 (commonly called zeolite X) is exchanged withan aqueous solution of mixed rare earth chlorides at l80F until thesodium content of the zeolite has been reduced to 0.5 wt. percent drybasis. The rare earth content calculated as oxide was 27.7 wt. percentdry basis. The rare earth exchanged zeolite (REX) is washed free ofsoluble salts and dried in air at 230F. The dried zeolite crystals areheated to a temperature (above about 500F) sufficient to facilitatecarbon deposits from a hydrocarbon stream. A stream of light gas oil ispassed over the crystals to achieve the deposition of about 2 wt.percent carbon. The sample is then cooled to room temperature and thensaturated with a hot concentrated solution of potassium perchlorate.This perchlorate saturated faujasite is subsequently dried at lowtemperature. Two grams of the dried perchlorate containing carbonizedfaujasite is compacted into a capsule fitted with heating wires and thenplaced in a gallon plastic bag container. Detonation is achieved bypassing an electric current through the heating wires. The fragmentedparticles generated by the detonation are subsequently swept 10 minuteperiod with nitrogen into a reaction vessel containing a wide rangeMid-Continent gas oil held at 900F. Products of catalytic conversiontaken overhead show a high degree of selective conversion of the gas oilto gasoline.

EXAMPLE 3 A crystalline aluminosilicate of the natural erionite type isfirst dehydrated at 1000F, then cooled to room temperature and contactedwith an alcoholic solution of nitroglycerin. The excess solution iswithdrawn from the natural crystalline aluminosilicate followed by lowtemperature drying under vacuum. This dried nitroglycerin-containingnatural crystalline aluminosilicate is used in the process forconverting hydrocarbons as described in Example 1.

I claim:

1. The method of preparing a finely divided zeolitic porous crystallinealuminosilicate which comprises impregnating into the pores of azeolitic porous crystalline aluminosilicate having a surface area of atleast 15 square meters per gram and a pore volume greater than 0.2 ccper gram with an explosivecomposition and detonatmg said explosivecomposition, whereby diffusivity in the crystalline aluminosilicate isenhanced.

2. The method of claim 1 wherein the detonation is conducted within aconfined zone.

3. The method of claim 1 wherein the impregnated porous solid isassociated with a heat absorbing material at the time of detonation.

4. The method of claim 3 wherein said heat absorbing material isselected from the class consisting of liquids which vaporize at theconditions of detonation, solids which melt at the conditions ofdetonation and solids which are converted to vapor at the conditions ofdetonation.

1. The method of preparing a finely divided zeolitic porous crystallinealuminosilicate which comprises impregnating into the pores of azeolitic porous crystalline aluminosilicate having a surface area of atleast 15 square meters per gram and a pore volume greater than 0.2 ccper gram with an explosive composition and detonating said explosivecomposition, whereby diffusivity in the crystalline aluminosilicate isenhanced.
 2. The method of claim 1 wherein the detonation is conductedwithin a confined zone.
 3. The method of claim 1 wherein the impregnatedporous solid is associated with a heat absorbing material at the time ofdetonation.